Detector for wireless systems



Dec. 8, 1925' 1,564,641

R. T. ST. JAMES DETECTOR FOR WIRELESS SYSTEMS Filed April 10, 1922 2/ lnummnnm.

Patented Dec. 8, 1925.

UNITED STATES PATENT OFF-ICE.

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. nn'rnc'ron lion wInnLnss sysrnnis i i Y Y I Application illed April 10, 1922. Serial No". 551,149.

To all whom it may concern: i Be it known that I, RoBnR'r T. ST. JAMES, a citizen of the United States, and

a resident of Chicago, county of Cook, and

5 State of'Illinois, have invented certain new and useful Improvements in a Detector for Wireless Systems; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, and to the letters of reference marked thereon, which form a part of this specification.

This invention relates to improvements in what are commonly known as detectors m the wireless telegraph and telephone art and consists of the matters hereinafter described and more particularly pointed out in the appended claims.

The ob eot f the invention is to provide a detector of great efliciency and of maximum sensitiveness, This and other objects and advantages of the invention will appear and be fully pointed out as I proceed with my ecificatlon. In the drawings:

Figure 1 is a side elevation of a detector ,tube embodying my invention;

Figure 2 is a perspectivev ew on an enlarged scale, showing the WlIll'lg ofv my 1mproved detector;

Fi re 3 represents a side elevation of the cold electrode of thedetector, viewed in the plane indicated by the line of Fig. 1;

Figure' l is a diagram1nat1c vlew representing a wireless receiving system including my improved detector.v

Referring to the draw1ngs:10 indicates the antenna of a wireless system and 11 mm- 'cates the air core transformer, the primary 11 of which is connected to ground at 12 and the secondary 11 of which is included in the indicator receiver circuit 13,--said receiver being shown in this case as a telephone receiver 14.

15 indicates the detector. usual exhausted glass tube or bulb 16, having sealed therein three conducting members or electrodes; namely, an electrode 17 which is to be heated; a normally cold electrode 18 and a control electrode 19 interposed between the two and commonly known as a grid in detectors of the kind heretofore used. 20 indicates the battery for heating the electrode 17, and 21 the battery in' circuit This is the between the cold electrode 18 and the telephone receiver 14. The circuits. described constitute a simple tube circuit and are as usual and familiar,-'th'eir relation and connection forming no part of the present invention.

Referring now to the detector itself The cold electrode 18 is in the form of a cylindrical sleeve,being a thin metal plate bent into cylindrical form... (See Fig. '2). The hot electrode 17 is afilament loop disposed approximately in the line of the central axis of the cold electrode 18.

The control electrode 19 is in the form of a helical coil surrounding the hot electrode filament 17 and supported at its bottom, but

entirely free of support at itstop. The.

wire of the coil is made heavy enough so that the several convolutions or loops of o the coil will stand, one aboveithe other, in their preliminary, determined, vertically spaced, relation without danger of contact between the parts ofproximate convolutions or loops and the resultant short-circuiting of one or more of said loops. The control coil is also rigid enough so that it will stand with its central axisvertical or substantially coincident with the central axis of the cold electrode, cylindrical plate 18, and so that there is no danger of the control coil falling against or contacting with the plate or with the'filamentand thereby temporarily bridging 'and short-circuiting the loops or convolutions of the coil.

For the best results and preferably, the

coil 19 and cylindrical plate 18 are so proportioned in diameter that the periphery of the coils is equidistant from the axis of the filament and from the inner surface of said plate. I

It appears that higher potentials can be built up on a helical coil, with its one end free and with its adjacent convolutions or loops free from contact with each other or from supporting connections adapted to bridge or short-circuit them. However this may be, I have found that with a coil of the kind, the added sensitiveness intended to be produced by the well-known grid heretofore used, is still further increased and raised to a maximum.

As shown in the drawings and preferably,

ing stem 19 which is secured in a short tube 19 sealed with the conductor 19, which connects with the coil, in the glass,

arm 23. This consists, as shown, of two wires twisted together at their bottom ends to provide a stifi? stem 23, which. is sealed in electrical connection with the conductor 23",

leading to the cold electrode in the sealing tube 22. Said wires are spread apart above thestem 23- to provide the tines or prongs 28 of the fork, which extend up to points at or adjacent to the top of the cylindrical plate 18, where their ends are attached, as by welding, to said plate. As shown, said prongs are hooked over the top edge of the plate, with their ends'welded to the inner surface of said plate. A narrow metal tongue 18", out along the bottom edge ofthe plate 18 and bent about the stem 23, provides, with the ends of the prongs of the forked wire arm 23, a three-point support for the cylindrical plate. This has been found to be amply sufiicient to hold the cold plate in proper, erect position with its axis verticalor coincident with the axis of the coil 19, and provides a simple and main electrodes, an insulating sealin by cheaply and quickly applied.

While in describing the invention I have referred to several details of mechanical construction and arrangement, it is to be understood that the invention is in no way limited thereto, except as pointed out in the appended claims.

I claim as my invention:

1. In a detector comprising an exhausted vessel, the two main electrodes therein, and a control electrode intermediate the said l for said vessel containing the con udtdi s leading to said electrodes, a short metal'tube sealed with one conductor in said plug and projecting above said plug,'and the control electrode having a stem depending into said metal tube, said tube providing a su port for and being secured-to the stem 0 said control electrode.

2. In a detector including an exhausted vessel, a conductor-carrying sealing plug for said vessel, a plate element in said vessel, an electrically conductive support for said plate element, consisting of a stem sealed in said plug and of laterally spaced, upwardly extending prongs attached to said plate element near its top, the plate element having a tongue formed at its bottom'edge and bent about said stem.

In testimony that I claim the foregoing as my invention, I afiix my signature this 5th day of April, A. D., 1922.

. ROBERT T. ST. JAMES. 

